Nebular Hypothesis Overview

Nebular Hypothesis

• Proposed by Immanuel Kant and Pierre-Simon Laplace in the 18th century
• A scientific theory explaining the formation of the solar system
• Suggests that the Sun, planets, and other celestial bodies formed from a rotating cloud of gas and dust called a nebula
• This nebula collapsed under its own gravity
• The collapse caused the nebula to spin faster and flatten into a spinning disk- shape
• The central region of this disk (the protosun) became increasingly dense and hot
• This resulted in nuclear fusion, creating the Sun
• The remaining material in the disk consisted of gas, dust, and solid particles (planetesimals)
• These planetesimals collided and merged through a process called accretion, gradually growing in size
• This formed larger bodies called protoplanets
• Protoplanets underwent differentiation
• Denser materials sank to the core, while lighter materials formed the mantle and crust
• This process generated heat, leading to a molten interior of some planets
• The theory is not without objections

Objections to the Nebular Hypothesis

• Planets hold 98% of the solar system's rotational energy, while the Sun holds 99.87% of the mass
• Heavy elements in Earth can only form at temperatures significantly higher than those on the Sun
• Some satellites rotate in a backward (retrograde) direction, and their speeds can exceed the rotation speed of their planets.